“Pesto” is so often the answer to “What do I do with these wilted herbs/carrot tops/abundance of basil?” It’s a good answer. Combining plant parts with cheese, garlic, pine nuts, and olive oil always makes for a tasty time, but pine nuts and parm are expensive, and making read-deal pesto often requires some amount of measuring. This is not the case with herb oil, pesto’s easier, cheaper, delicious stepsister.
The oil is loosely based on Julia Turshen’s green sauce, only there are no measurements, no ratios, no rules. Add handfuls of herbs to a food processor or blender, along with a garlic clove if you desire such, and pulse until they are pretty well pulverized. Add a pinch of salt and then, with the motor running and the blades whirring, drizzle in olive oil until you get the consistency you’re looking for, be it spreadable or pourable. Taste your oil and season more if needed.
You can of course add cheese if you want it, but you can also add a squeeze of lemon, or a spoonful of lemon zest, or a pinch of chili powder. You can also use a different oil entirely. Pistachio would be good. You can use one herb or five. I made my herb oil with some oregano, chives, and tarragon, and it ruled. If you’re looking to get rid of some carrot tops, beet greens, or wilted scallions, you can toss those in there, too. As I said, there are no rules with herb oil.
Once your oil is made, use it immediately, and use it liberally. Use it as you would pesto—on bread, on eggs, as a cheap and easy pasta sauce, on grilled meats and vegetables, or swirl it into some labneh or sour cream to make dip. You have a lot of options. (One option you do not have, however, is long-term storage, as botulism is a risk with plant-infused oils. This means you’ll have to use your herb oil all at once, but that shouldn’t be a problem.)